linux-kernel - Re: [PATCH] x86/mm: fix __swp_entry_to

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Date:   Mon, 8 May 2023 14:23:11 +0200
From:   Juergen Gross <jgross@...e.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] x86/mm: fix __swp_entry_to_pte() for Xen PV guests

PING (3rd one, after 2 months of getting no feedback)!

I'm inclined to carry it just via the Xen tree if x86 maintainers continue
to ignore it ...


Juergen

On 06.03.23 13:32, Juergen Gross wrote:
> Normally __swp_entry_to_pte() is never called with a value translating
> to a valid PTE. The only known exception is pte_swap_tests(), resulting
> in a WARN splat in Xen PV guests, as __pte_to_swp_entry() did
> translate the PFN of the valid PTE to a guest local PFN, while
> __swp_entry_to_pte() doesn't do the opposite translation.
> 
> Fix that by using __pte() in __swp_entry_to_pte() instead of open
> coding the native variant of it.
> 
> For correctness do the similar conversion for __swp_entry_to_pmd().
> 
> Fixes: 05289402d717 ("mm/debug_vm_pgtable: add tests validating arch helpers for core MM features")
> Signed-off-by: Juergen Gross <jgross@...e.com>
> ---
>   arch/x86/include/asm/pgtable_64.h | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/include/asm/pgtable_64.h b/arch/x86/include/asm/pgtable_64.h
> index 7929327abe00..a629b1b9f65a 100644
> --- a/arch/x86/include/asm/pgtable_64.h
> +++ b/arch/x86/include/asm/pgtable_64.h
> @@ -237,8 +237,8 @@ static inline void native_pgd_clear(pgd_t *pgd)
>   
>   #define __pte_to_swp_entry(pte)		((swp_entry_t) { pte_val((pte)) })
>   #define __pmd_to_swp_entry(pmd)		((swp_entry_t) { pmd_val((pmd)) })
> -#define __swp_entry_to_pte(x)		((pte_t) { .pte = (x).val })
> -#define __swp_entry_to_pmd(x)		((pmd_t) { .pmd = (x).val })
> +#define __swp_entry_to_pte(x)		(__pte((x).val))
> +#define __swp_entry_to_pmd(x)		(__pmd((x).val))
>   
>   extern void cleanup_highmap(void);
>   


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